1. Field of the Invention
This invention relates to the preparation of novel heterocyclic compounds and compositions containing them and, more particularly, is concerned with the preparation of bis(cyclic ureas) which can act as masked diisocyanates, with stable one-component polyurethane forming systems containing said bis(cyclic ureas), and with processes for preparing polyurethane therefrom.
2. Description of the Prior Art
U.S. Pat. No. 4,138,398 discusses the applicable prior art (not repeated herein in the interest of brevity) and discloses a series of bis(cyclic ureas) having the following formula: ##STR3## in which C.sub.n' H.sub.2n' represents alkylene from 4 to 12 carbon atoms, inclusive, and in which there are at least 4 carbons in the chain separating the two N atoms and R is a divalent radical represented by ##STR4## The compounds (I) are shown to function as masked diisocyanates in that, upon heating to temperatures of 100.degree. C. or higher, they undergo ring opening to form the corresponding diisocyanate of the formula EQU OCN--C.sub.n' H.sub.2n' --NH--R--NH--C.sub.n' H.sub.2n' --NCO (II)
where R and C.sub.n' H.sub.2n' have the meaning defined above.
Because of this ability to generate a diisocyanate on heating, the compounds (I) are admixed with an appropriate polyol and employed as compositions which are stable on storage at ambient temperature (circa 25.degree. C.) but which, upon heating to a temperature above that at which the compounds (I) undergo ring-opening, generate a polyurethane by reaction of the liberated diisocyanate with the polyol
We have now found that compounds closely related to those of formula (I) above possess properties which are significantly different from those of formula (I) and these differences give rise to unexpected advantages in the use of the compounds of this invention as compared with the corresponding use of the compounds of formula (I).